|Tait Jr, Richard|
|Cushman, Robert - Bob|
|Smith, Timothy - Tim|
Submitted to: Theriogenology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2018
Publication Date: 6/1/2018
Citation: Tait Jr, R.G., Cushman, R.A., McNeel, A.K., Casas, E., Smith, T.P.L., Freetly, H.C., Bennett, G.L. 2018. µ-Calpain (CAPN1), calpastatin (CAST), and growth hormone receptor (GHR) genetic effects on Angus beef heifer performance traits and reproduction. Theriogenology. 113:1-7. https://doi.org/10.1016/j.theriogenology.2018.02.002.
Interpretive Summary: Genetic markers within the µ-calpain (CAPN1) and calpastatin (CAST) genes have been previously associated with beef tenderness. Also, genetic markers within the growth hormone receptor (GHR) gene have been associated with milk yield and milk composition traits in dairy cattle and body composition traits in beef cattle. Those previous survey studies often ignored animals with two copies of the rare allele because of low frequency of that genotype. These genetic markers have very little information about potential adverse effects on female performance in an extensive beef production system. Multiyear selection increased the frequency of animals with the rare genotypes enabling more accurate estimation of genetic effects. The GHR genetic marker was associated with body weights of beef females, with the heterozygous genotype being lighter which would reduce maintenance energy requirements. Also, the CAPN1 genetic markers were found to have an antagonism between beef tenderness and calving day, with the tough genotype being associated with cows that calve earlier in the calving season. Information about these effects will be important for beef geneticists and producers to develop marker assisted management strategies and to account for antagonisms between beef quality traits and cow productivity traits.
Technical Abstract: Genetic marker effects and type of inheritance are estimated with poor precision when minor marker allele frequencies are low. An Angus population was subjected to marker assisted selection for multiple years to equalize CAPN1 haplotypes, CAST, and GHR genetic marker frequencies. The objective was to estimate the pleiotropic effects of these carcass quality oriented markers for body weight, reproduction, and first calf performance traits in 174 replacement beef females which were managed under 2 postweaning development protocols. Heifers were weighed at 11-, 12-, and 13-mo, at first breeding season pregnancy evaluation, and prior to first calving season. Pubertal status was determined at 11-, 12-, and 13-mo of age. Antral follicles were counted, reproductive tracts were scored, and tract dimensions were measured at 13-mo. Body condition and hip height were scored and measured at pregnancy evaluation and prior to calving season. Heifer pregnancy and weaning rates and ordinal birth date were recorded. Calf body weights at birth and weaning were analyzed. Single df linear contrasts for recessive effects of the GHR heterozygous genotype showed significant decreases of 2.5e3.6% in 11-, 12-, and 13-mo heifer body weights and heifer weight prior to calving. The additive differences between GHR homozygotes were small and not significant for all body weights measured but a 1 wk difference in calf birth date was significant. For all 13-mo uterine measurements, scores, and antral follicle counts, only the CAST dominance contrast for medium antral follicle count was significant. The CAPN1 haplotype with a strong additive effect for increased beef tenderness also had a significant additive effect on calving date. Heifers homozygous for the tender haplotype calved 7.9 days later than heifers homozygous for the tough haplotype. Most heifer reproductive traits were not significantly affected by CAST and CAPN1 markers that are widely used to improve beef tenderness by selection and breeders should not be concerned with how these markers affect reproduction and other heifer traits with the possible exception of CAPN1 effects on calving date.